Saturday, October 31, 2015

DIY Canard Airframe 04

Woot! First time out with the laser cutter. Unfortunately, the holes that I meant for the bracing to go through were too small for the piece of wood meant to go through it... looks like I'm going to have to make another trip down. If not, it was a very successful run.


I spoke to hastly. The holes were too small, because the entire object was printed at about 88.8% of full scale! Darn it. I was wondering why the battery fit so snugly when I had planned for lots of space. Only then did I measure it, and realized that there was a size discrepancy.

If so, then the weight for the full fuselage will far surpass my original design estimates, and if I continue down this path, will have an airframe with much higher wing loading.

I need to think how to proceed. Very likely I will just proceed, as I do hope to learn more about creating a canard.

The original idea behind the wood frame, is to have a strong underlying structure, as the foam weakens significantly with holes cut into it.

Let us ponder.

Edit 2:
Didn't want to make a new post. I stuck the whole thing together with Titebond III .As I didn't have any clamps, I just relied on the thick rubber bands used to hold down the wing to hold the pieces together.

Titebond is a pleasure to work with, while the working time _could_ be longer, it was good enough for the few pieces I had to cludge together. In addition, it clean up with water! Some people have mentioned that it doesn't sand as well as Titebond III, but I don't think I will need to sand much as it just wipes away with a damp paper towel. And it washes off in the toilet, easy!

The strength of the glue is extremely impressive. I did some test with some waste plywood pieces and the glue of the veneers gave way before the glue bond. That's extremely impressive. The assembled fuselage otoh feels extremely rigid, and that's before I even put in my extra bracing.

I think I will just go ahead with the build. My motor is theoretically able to give about 600g of thrust with an APC 8x4E prop, and if the aircraft comes in about 800g, the thrust to weight ration _should_ be fine.

In the unlikely event that I would need more thrust, swapping to a 9x3.8SF will give over 800g of thrust, at the expense of flight time. In my limited experience so far, all my designs have take off at perhaps 60-70% on the throttle, and I can usually fly around half throttle, so it's very likely I will have enough thrust on just the 8x4E.

Quite excited to see how this build goes, but I am also very tired as I could not sleep well last night, kept waking up ever so often. Argh.

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